This invention is directed to devices and methods for generating electromagnetic radiation, including visible, ultra-violet, and infrared, with electrodeless plasma lamps. The present invention provides plasma lamps driven by a radio-frequency source without the use of electrodes inside a gas-filled vessel (bulb). More particularly the invention involves the creation of an array of electrodeless plasma lamps. Such array of electrodeless plasma lamps can be applied to applications such as stadiums, security, parking lots, military and defense, streets, large and small buildings, vehicle headlamps, aircraft landing, bridges, warehouses, UV water treatment, UV epoxy curing, semiconductor processing, annealing, heating, agriculture, architectural lighting, stage lighting, medical illumination, projectors and displays, as well as similar applications.
Plasma lamps provide extremely bright, broadband light, and are useful in applications such as general illumination, projection systems, and industrial processing. The typical plasma lamp manufactured today contains a mixture of gas and trace substances that is excited to form a plasma using a high current passed through closely-spaced electrodes. This arrangement, however, suffers from deterioration of the electrodes, and therefore a limited lifetime.
Electrodeless plasma lamps driven by microwave sources overcome problems associated with electrode deterioration and result in lamps with longer lifetimes, stable spectrums, and higher efficiencies. Conventional configurations include a plasma fill encased either in a bulb or a sealed recess within a dielectric body forming a waveguide, with microwave energy being provided by a source such as a solid-state power amplifier or a magnetron and introduced into the waveguide and heating the plasma resistively. Other examples are provided by U.S. Patent Application No. 20090322240A1 and U.S. Pat. Nos. 7,291,985, 7,362,056, and 6,737,809, each of which are incorporated by reference herein. To achieve higher electromagnetic radiation output from the electrodeless plasma lamps (higher lumens for example), larger bulbs and higher power RF sources are desirable. While microwave sources such magnetron are available with RF powers exceeding 1000 W in a compact form factor, magnetrons do not have the reliability of solid-state power amplifiers. Although it may be possible to achieve higher RF output power from solid-state power amplifiers by combining a number of them, it can result in RF losses through the combiner and impact the overall efficiency of the RF source. Using power amplifiers at lower frequency of operation can improve the efficiency of the power amplifier. Use of a larger bulb also improves coupling RF energy to the bulb at lower operating frequencies, but it is difficult to optimize the performance of the system for best efficiency of the power amplifier and optimum coupling to the bulb. Furthermore in some applications it is difficult, if not impossible, to achieve uniform electromagnetic distribution from a large single bulb. Furthermore the power supplies required for some high lumens/electromagnetic radiation applications are bulky and inefficient. Also in some applications it is desirable to have the ability to change the lighting conditions (color temperature, CRI, distribution, etc.).
From above, it is seen that techniques for improved lighting are highly desired.